This invention is concerned with wind-driven electric generators of the downwind type having flexible blades capable of downwind coning and pitch control by a collective pitch mechanism.
Wind-driven electric generators, commonly referred to as "wind turbines," have proved their ability to generate substantial amounts of electricity in proper operating environments. However, most wind turbines presently in use are heavy machines with rigid blades and are expensive to manufacture and maintain. Because of their rigidity, structural loads tend to be very high, and the entire wind turbine must be heavy enough and strong enough to withstand such loads.
Structural loads can be reduced by designing flexibility or compliance in the wind turbine rotor.
Examples of downwind wind turbines with flexible blades are described in U.S. Pat. No. 5,178,518 issued Jan. 12, 1993 to Carter, Sr., U.S. Pat. No. 4,431,375 issued Feb. 14, 1984 to Carter, Jr. et al, and U.S. Pat. No. 4,366,387 issued Dec. 28, 1982 to Carter, Jr., et al, all of which are incorporated herein by reference.
It is desirable that the wind turbine be constructed in a manner that takes maximum benefit of blade flexibility and weight reduction, while providing high strength and reduced manufacturing and maintenance costs. Also, it is desirable that the wind turbine be constructed to run only when operating conditions are appropriate. The present invention provides such wind turbines.